This invention relates to a biometric information processing device for authenticating individuals, and more specifically, to an authentication technique using venous information of a living body.
Security of personal information is gaining greater importance in recent years. Biometrics authentication is attracting attention as individual authentication technology for ensuring security. Biometrics authentication is authentication technology that uses physiological information of a person, and is excellent in terms of convenience and preservation of confidentiality.
Examples of known conventional biometrics authentication technology include authentication using a fingerprint, iris, voice, face, or vein on the back of a hand or on the palm side of a finger. In particular, vein biometric authentication using a vein is highly fraud-proof in terms of use of in vivo information.
The description given below focuses on finger vein authentication devices.
A finger vein authentication device first irradiates a finger with infrared light, which is scattered inside the finger and then transmitted to the outside. The finger vein authentication device picks up the infrared light transmitted through the palm side of the finger.
Since hemoglobin in blood absorbs infrared light more than its surrounding tissues, the image picked up by the finger vein authentication device is a visualization of blood vessels running under the skin on the palm side of the finger (i.e., finger veins) as a dark shadow pattern (i.e., finger vein pattern).
Features of the finger vein pattern are registered in the finger vein authentication device in advance.
For authentication, the finger vein authentication device picks up an image of the user's finger. The finger vein authentication device accomplishes individual authentication by obtaining a correlation between a finger vein pattern of the image picked up and the features registered in advance.
However, conventional finger vein authentication devices pick up an image of a finger inserted into the finger vein authentication devices. Therefore, users feel reluctant to insert a finger into the closed interior space of a finger vein authentication device.
Conventional finger vein authentication devices need to be tall enough to accommodate a light source placed beside a finger as disclosed in JP 2004-265269 A. The applicant of this application has filed a patent application for a contrasting system which uses in authentication a spectrum measured with a light source and a detector that are placed on the same side as a measurement subject living body.
With the background art described above, accurate authentication is not possible in a case where a finger presented for matching is positioned differently from when it is registered, thus casting a different pattern from the image picked up upon registration. A structure for regulating the finger position is therefore necessary in order to improve the authentication accuracy. This takes form as finger rests and other physical structures for directing where to place a finger in a device disclosed in JP 2004-265269 A.
A configuration disclosed in PCT/JP2005/011184 enables an authentication device to have a small size, but its substantially flat surface on which a living body is placed makes it difficult to add finger rests and other similar physical structures. Without such structures, users have no way of knowing the right place to put a living body, and the position difference between registered biometric information and biometric information presented for authentication leads to incorrect authentication.